#include <cstdio>
#include <cmath>

bool is_prime(int x);

int main(int argc, char const *argv[]){
    int input_num;
    while(scanf("%d", &input_num) != EOF)
        puts(is_prime(input_num) ? "yes" : "no");
    return 0;
}

bool is_prime(int x){
    if (x <= 1)
        return false;
    int bound = (int)sqrt(x) + 1; // time save: do not use sqrt() in loop
    for (int i = 2; i < bound; i++){
        if (x % i == 0){
            return false;
        }
    }
    return true;
}